* Tested under NetBSD/amd64 6.99.28 and Debian GNU/Linux/amd64 7.3
Changelog:
From: http://llvm.org/svn/llvm-project/llvm/tags/RELEASE_34/final/docs/ReleaseNotes.rst
Non-comprehensive list of changes in this release
=================================================
* This is expected to be the last release of LLVM which compiles using a C++98
toolchain. We expect to start using some C++11 features in LLVM and other
sub-projects starting after this release. That said, we are committed to
supporting a reasonable set of modern C++ toolchains as the host compiler on
all of the platforms. This will at least include Visual Studio 2012 on
Windows, and Clang 3.1 or GCC 4.7.x on Mac and Linux. The final set of
compilers (and the C++11 features they support) is not set in stone, but we
wanted users of LLVM to have a heads up that the next release will involve
a substantial change in the host toolchain requirements.
* The regression tests now fail if any command in a pipe fails. To disable it in
a directory, just add ``config.pipefail = False`` to its ``lit.local.cfg``.
See :doc:`Lit <CommandGuide/lit>` for the details.
* Support for exception handling has been removed from the old JIT. Use MCJIT
if you need EH support.
* The R600 backend is not marked experimental anymore and is built by default.
* ``APFloat::isNormal()`` was renamed to ``APFloat::isFiniteNonZero()`` and
``APFloat::isIEEENormal()`` was renamed to ``APFloat::isNormal()``. This
ensures that ``APFloat::isNormal()`` conforms to IEEE-754R-2008.
* The library call simplification pass has been removed. Its functionality
has been integrated into the instruction combiner and function attribute
marking passes.
* Support for building using Visual Studio 2008 has been dropped. Use VS 2010
or later instead. For more information, see the `Getting Started using Visual
Studio <GettingStartedVS.html>`_ page.
* The Loop Vectorizer that was previously enabled for ``-O3`` is now enabled
for ``-Os`` and ``-O2``.
* The new SLP Vectorizer is now enabled by default.
* ``llvm-ar`` now uses the new Object library and produces archives and
symbol tables in the gnu format.
* FileCheck now allows specifing ``-check-prefix`` multiple times. This
helps reduce duplicate check lines when using multiple RUN lines.
* The bitcast instruction no longer allows casting between pointers
with different address spaces. To achieve this, use the new addrspacecast
instruction.
* Different sized pointers for different address spaces should now
generally work. This is primarily useful for GPU targets.
* OCaml bindings have been significantly extended to cover almost all of the
LLVM libraries.
Mips Target
-----------
Support for the MIPS SIMD Architecture (MSA) has been added. MSA is supported
through inline assembly, intrinsics with the prefix '``__builtin_msa``', and
normal code generation.
For more information on MSA (including documentation for the instruction set),
see the `MIPS SIMD page at Imagination Technologies
<http://imgtec.com/mips/mips-simd.asp>`_
PowerPC Target
--------------
Changes in the PowerPC backend include:
* fast-isel support (for faster ``-O0`` code generation)
* many improvements to the builtin assembler
* support for generating unaligned (Altivec) vector loads
* support for generating the fcpsgn instruction
* generate ``frin`` for ``round()`` (not ``nearbyint()`` and ``rint()``, which
had been done only in fast-math mode)
* improved instruction scheduling for embedded cores (such as the A2)
* improved prologue/epilogue generation (especially in 32-bit mode)
* support for dynamic stack alignment (and dynamic stack allocations with large alignments)
* improved generation of counter-register-based loops
* bug fixes
SPARC Target
------------
The SPARC backend got many improvements, namely
* experimental SPARC V9 backend
* JIT support for SPARC
* fp128 support
* exception handling
* TLS support
* leaf functions optimization
* bug fixes
SystemZ/s390x Backend
---------------------
LLVM and clang can now optimize for zEnterprise z196 and zEnterprise EC12
targets. In clang these targets are selected using ``-march=z196`` and
``-march=zEC12`` respectively.
From: http://llvm.org/svn/llvm-project/cfe/tags/RELEASE_34/final/docs/ReleaseNotes.rst
What's New in Clang 3.4?
========================
Some of the major new features and improvements to Clang are listed here.
Generic improvements to Clang as a whole or to its underlying infrastructure
are described first, followed by language-specific sections with improvements
to Clang's support for those languages.
Last release which will build as C++98
--------------------------------------
This is expected to be the last release of Clang which compiles using a C++98
toolchain. We expect to start using some C++11 features in Clang starting after
this release. That said, we are committed to supporting a reasonable set of
modern C++ toolchains as the host compiler on all of the platforms. This will
at least include Visual Studio 2012 on Windows, and Clang 3.1 or GCC 4.7.x on
Mac and Linux. The final set of compilers (and the C++11 features they support)
is not set in stone, but we wanted users of Clang to have a heads up that the
next release will involve a substantial change in the host toolchain
requirements.
Note that this change is part of a change for the entire LLVM project, not just
Clang.
Major New Features
------------------
Improvements to Clang's diagnostics
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Clang's diagnostics are constantly being improved to catch more issues, explain
them more clearly, and provide more accurate source information about them. The
improvements since the 3.3 release include:
- -Wheader-guard warns on mismatches between the #ifndef and #define lines
in a header guard.
.. code-block:: c
#ifndef multiple
#define multi
#endif
returns
`warning: 'multiple' is used as a header guard here, followed by #define of a different macro [-Wheader-guard]`
- -Wlogical-not-parentheses warns when a logical not ('!') only applies to the
left-hand side of a comparison. This warning is part of -Wparentheses.
.. code-block:: c++
int i1 = 0, i2 = 1;
bool ret;
ret = !i1 == i2;
returns
`warning: logical not is only applied to the left hand side of this comparison [-Wlogical-not-parentheses]`
- Boolean increment, a deprecated feature, has own warning flag
-Wdeprecated-increment-bool, and is still part of -Wdeprecated.
- Clang errors on builtin enum increments and decrements.
.. code-block:: c++
enum A { A1, A2 };
void test() {
A a;
a++;
}
returns
`error: must use 'enum' tag to refer to type 'A'`
- -Wloop-analysis now warns on for-loops which have the same increment or
decrement in the loop header as the last statement in the loop.
.. code-block:: c
void foo(char *a, char *b, unsigned c) {
for (unsigned i = 0; i < c; ++i) {
a[i] = b[i];
++i;
}
}
returns
`warning: variable 'i' is incremented both in the loop header and in the loop body [-Wloop-analysis]`
- -Wuninitialized now performs checking across field initializers to detect
when one field in used uninitialized in another field initialization.
.. code-block:: c++
class A {
int x;
int y;
A() : x(y) {}
};
returns
`warning: field 'y' is uninitialized when used here [-Wuninitialized]`
- Clang can detect initializer list use inside a macro and suggest parentheses
if possible to fix.
- Many improvements to Clang's typo correction facilities, such as:
+ Adding global namespace qualifiers so that corrections can refer to shadowed
or otherwise ambiguous or unreachable namespaces.
+ Including accessible class members in the set of typo correction candidates,
so that corrections requiring a class name in the name specifier are now
possible.
+ Allowing typo corrections that involve removing a name specifier.
+ In some situations, correcting function names when a function was given the
wrong number of arguments, including situations where the original function
name was correct but was shadowed by a lexically closer function with the
same name yet took a different number of arguments.
+ Offering typo suggestions for 'using' declarations.
+ Providing better diagnostics and fixit suggestions in more situations when
a '->' was used instead of '.' or vice versa.
+ Providing more relevant suggestions for typos followed by '.' or '='.
+ Various performance improvements when searching for typo correction
candidates.
- `LeakSanitizer <LeakSanitizer.html>`_ is an experimental memory leak detector
which can be combined with AddressSanitizer.
New Compiler Flags
------------------
- Clang no longer special cases -O4 to enable lto. Explicitly pass -flto to
enable it.
- Clang no longer fails on >= -O5. These flags are mapped to -O3 instead.
- Command line "clang -O3 -flto a.c -c" and "clang -emit-llvm a.c -c"
are no longer equivalent.
- Clang now errors on unknown -m flags (``-munknown-to-clang``),
unknown -f flags (``-funknown-to-clang``) and unknown
options (``-what-is-this``).
C Language Changes in Clang
---------------------------
- Added new checked arithmetic builtins for security critical applications.
C++ Language Changes in Clang
-----------------------------
- Fixed an ABI regression, introduced in Clang 3.2, which affected
member offsets for classes inheriting from certain classes with tail padding.
See Bug16537.
- Clang 3.4 supports the 2013-08-28 draft of the ISO WG21 SG10 feature test
macro recommendations. These aim to provide a portable method to determine
whether a compiler supports a language feature, much like Clang's
|has_feature macro|_.
.. |has_feature macro| replace:: ``__has_feature`` macro
.. _has_feature macro: LanguageExtensions.html#has-feature-and-has-extension
C++1y Feature Support
^^^^^^^^^^^^^^^^^^^^^
Clang 3.4 supports all the features in the current working draft of the
upcoming C++ standard, provisionally named C++1y. Support for the following
major new features has been added since Clang 3.3:
- Generic lambdas and initialized lambda captures.
- Deduced function return types (``auto f() { return 0; }``).
- Generalized ``constexpr`` support (variable mutation and loops).
- Variable templates and static data member templates.
- Use of ``'`` as a digit separator in numeric literals.
- Support for sized ``::operator delete`` functions.
In addition, ``[[deprecated]]`` is now accepted as a synonym for Clang's
existing ``deprecated`` attribute.
Use ``-std=c++1y`` to enable C++1y mode.
OpenCL C Language Changes in Clang
----------------------------------
- OpenCL C "long" now always has a size of 64 bit, and all OpenCL C
types are aligned as specified in the OpenCL C standard. Also,
"char" is now always signed.
Internal API Changes
--------------------
These are major API changes that have happened since the 3.3 release of
Clang. If upgrading an external codebase that uses Clang as a library,
this section should help get you past the largest hurdles of upgrading.
Wide Character Types
^^^^^^^^^^^^^^^^^^^^
The ASTContext class now keeps track of two different types for wide character
types: WCharTy and WideCharTy. WCharTy represents the built-in wchar_t type
available in C++. WideCharTy is the type used for wide character literals; in
C++ it is the same as WCharTy, but in C99, where wchar_t is a typedef, it is an
integer type.
Static Analyzer
---------------
The static analyzer has been greatly improved. This impacts the overall analyzer quality and reduces a number of false positives.
In particular, this release provides enhanced C++ support, reasoning about initializer lists, zeroing constructors, noreturn destructors and modeling of destructor calls on calls to delete.
Clang Format
------------
Clang now includes a new tool ``clang-format`` which can be used to
automatically format C, C++ and Objective-C source code. ``clang-format``
automatically chooses linebreaks and indentation and can be easily integrated
into editors, IDEs and version control systems. It supports several pre-defined
styles as well as precise style control using a multitude of formatting
options. ``clang-format`` itself is just a thin wrapper around a library which
can also be used directly from code refactoring and code translation tools.
More information can be found on `Clang Format's
site <http://clang.llvm.org/docs/ClangFormat.html>`_.
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